Plants are ideally suited to study the genetic response of higher eukaryotes to environmental change. Somatic cell genetics will be used to study the ability of soybean: (A) to utilize allantoin as a sole source of nitrogen and (B) to develop cellular resistance to heavy metals or inhibitors of fatty acid or pyrimidine biosynthesis. The proposal is divided into three sections: 1) The development of a system of somatic cell genetics which is partially completed as a result of past work; 2) The isolation and genetic analysis of structural and regulatory mutants defective, or altered, in allantoin metabolism; 3) The genetic analysis of resistance to the inhibitors: Cerulenin, Cadmium and PALA. For the first three years, labor intensive work will concentrate on developing a somatic genetic mapping system, which will include: markers for identifying chromosomes (isozymes, monoclonal antibodies, and DNA polymorphisms); a set of marker cell lines, including monosomics lacking specific chromosomes and haploid lines carrying insertions for resistance to the antibiotic G-418; and mapping by fusion followed by chromosome loss induced by the carbamate derivative, CIPC. Two additional projects will assume increasing importance and occupy most of the effort of the last two years. The genetic analysis of allantoin utilization will use the somatic genetic system to isolate and map the structural and regulatory genes involved in this pathway of nitrogen utilization. Expression of yeast genes in soybean will be attempted (and vice versa). Resistance of Cadmium, Cerulenin, or PALA will be studied as models for the selection of quantitative traits which may reflect the selection of cellular resistance, eventually expressed as resistance of the entire plants.